What dose of hydrocortisone (steroids) should be given prior to initiating thyroxine (levothyroxine) therapy, and should it be administered intravenously (IV) or orally?

Steroid Dosing Before Thyroxine Administration in Adrenal Insufficiency

Hydrocortisone 100 mg IV should be administered before initiating thyroxine therapy, and thyroxine should be given orally once the patient is stabilized on steroid replacement. 1

Steroid Dosing Protocol

When initiating thyroxine in a patient with suspected or confirmed adrenal insufficiency, the following approach should be taken:

Initial Steroid Coverage

• Primary or secondary adrenal insufficiency: Administer hydrocortisone 100 mg IV initially 1
• Follow with maintenance dosing of hydrocortisone 15-20 mg daily in divided doses (typically 2/3 in morning, 1/3 in early afternoon) 1
• For severe symptoms or adrenal crisis: Consider continuous IV infusion of hydrocortisone at 200 mg/24 hours 1, 2

Timing of Thyroxine Administration

• Always start corticosteroids several days before thyroid hormone to prevent precipitating adrenal crisis 1
• This is critical as initiating thyroid replacement without adequate steroid coverage can trigger an adrenal crisis due to increased metabolic demands

Route of Administration

Steroids

• Initial dose: Intravenous (IV) hydrocortisone 100 mg 1
• Maintenance: Oral hydrocortisone once patient is stabilized

Thyroxine

• Route: Oral levothyroxine is the preferred route for maintenance therapy 1
• Dosing: Weight-based dosing of levothyroxine
• Monitoring: Follow free T4 levels for thyroid hormone replacement titration (TSH is not accurate in central hypothyroidism) 1

Special Considerations

Adrenal Crisis Prevention

• Patients need education on stress dosing for illness (doubling doses during illness) 1
• Medical alert bracelet for adrenal insufficiency is recommended 1
• Endocrine consultation prior to any procedures for stress-dose planning 1

Monitoring Therapy

• For central hypothyroidism (as in hypophysitis), TSH is not reliable for monitoring - use free T4 instead 1
• Titrate hydrocortisone to a maximum of 30 mg daily total dose for residual symptoms of adrenal insufficiency 1

Common Pitfalls to Avoid

1. Never start thyroxine before adequate steroid coverage - this can precipitate adrenal crisis 1
2. Don't rely on TSH for monitoring in central hypothyroidism - follow free T4 levels 1
3. Don't underestimate the need for stress dosing during illness or procedures 1
4. Avoid single daily dosing of hydrocortisone - this fails to mimic the natural cortisol rhythm and may lead to suboptimal outcomes 3

By following this protocol, you can safely initiate thyroxine therapy while minimizing the risk of precipitating an adrenal crisis in patients with adrenal insufficiency.